March 15, 2019 by Mark Hathaway, University of Otago
A University of Otago study has shown the positive impact bird poo, or guano, has on coral growth in tropical seas. Published online in the respected scientific journal Scientific Reports, the study Seabird nutrients are assimilated by corals and enhance coral growth rates demonstrates that seabird nutrients can significantly boost coral growth rates, offering a positive news story in a decade that has documented dramatic declines in reef health and percentage cover.
"The findings have important implications for catchment-to-reef connectivity and demonstrate that coral conservation should also consider catchment management in addition to marine protection," says author Dr. Candida Savage, of Otago's Department of Marine Science.
The research was conducted in two Fiji marine protected areas; one remote island (Namena) with an intact coastal forest with breeding seabirds, the other (Cousteau) is away from any seabirds and their associated guano. Natural chemical tracers in coral tissues showed that corals growing near the roosting seabirds took up seabird nutrients. A one-year growth experiment demonstrated that corals grew up to four times faster at the Namena reef compared to the Cousteau reef due to the presence of seabirds.
"Bird guano is known for its qualities as a fertiliser, however the impact it had on coral growth has been unknown until now. I was astounded at how much of a difference the presence of guano had in promoting coral growth," Dr. Savage says. The research shows that natural sources of nutrients like seabird guano may benefit coral reefs, in contrast to man-made nutrients from land that tend to degrade coral reefs.